The primary aims of the Junior Scholar Development Core are to: (1) to support career development of those recently acquiring doctoral degrees who seek to build research programs relating to network and neighborhood effects on health; (2) stimulate new research in the area of social network and geographic neighborhood effects on health and health care, particularly relating to the themes that are emphasized in this Program Project (e.g., the description of social networks of patients and providers, the effects of health linkages on health outcomes, the interplay of geographic clustering and health outcomes, and the role of social context variables in determining health); and (3) to foster an environment that emphasizes learning and development across research projects and cores, especially in the areas described in Aim 2. We also hope to increase attention to these topics more broadly at Harvard University. In connection with these three aims, the Junior Scholar Development Core will provide salary support for post-doctoral research fellows and funds for small-scale pilot research conducted by those fellows and by junior faculty who apply. Core C will also fund career development activities that afford opportunities for learning and exchange of ideas, such as travel to scientific conferences. Through this initiative, we aim to increase the number of researchers involved in the study of social network and neighborhood effects on health so that the topic becomes and remains an important component of the increasing body of research on the social context of health and health care delivery. Core C will also provide post-doctoral level scientific personnel for the individual projects within this Program Project effort by matching fellows with on-going research projects. By administering the funding for post-doctoral research positions centrally in Core C, we will be able to most efficiently meet our twin goals of (1) fostering the individual interests and research agendas of post-doctoral fellows, and (2) matching these fellows with research project faculty whose projects would benefit from their skills and interests. Integrating the Small Grants Program with the Post-Doctoral Fellowship Program will promote maximal cross-fertilization among research projects of junior scholars. We are confident that the existence of Core C will result in a dynamic research climate within the Program Project, energized by new ideas from an outstanding group of young scientists from a broad array of scientific disciplines.